Abstract
Using combined neutron spectroscopy and first-principles calculations, we investigated the electronic structure and vibrational dynamics of the recently discovered class of ternary hydrides ( and Ge). In these compounds, all hydrogen atoms are located in a single type of -defined octahedral site. The atoms form long-range chains sandwiched between each -octahedra layer. The Li-H interactions are strongly ionic, with bond lengths comparable to those in LiH. Our density functional theory calculations indicate that Li atoms transfer their electrons to both H and atoms. atoms within the chain are bonded covalently. The electronic density of states reveals that both hydrides exhibit metallic behavior. The observed vibrational spectra of these hydrides are in good overall agreement with the calculated phonon modes. There is evidence of dispersion induced splitting in the optical phonon peaks that can be ascribed to the coupling of H vibrations within the -octahedra layers.
- Received 21 May 2007
- Accepted 7 August 2007
DOI:https://doi.org/10.1103/PhysRevB.76.224301
©2007 American Physical Society